I think that would depend on your definition of "quality." I haven't read more than 20% of my friends list since about a week after I got my journal. I haven't noticed a drop in quality, because I don't think there was much there to begin with. The whole point of LJ is so boring people can write about their boring lives, and that's what we do. If we were Pulitzer Prize-winning novelists, we wouldn't be wasting our dynamic and fascinating autobiographical anecdotes on LJ.

It's only dull if you don't give two plops about who and what you're reading, which is probably the reason I ignore at least 80% of it.